Snap switch



E. R'. ROSWELL SNAP SWITCH June 27, 1950 2 Sheets-Sheet 1 Filed Dec. 22,1945 5 3a 6 [IR 40 Earzefll oswezz,

uqffirnegy June 27, 1950 E. R. ROSWELL 2,513,053

SNAP SWITCH Filed Dec. 22, 1945 2 Sheets-Sheet 2 Patented June 27, 1950SNAP SWITCH Earle B. Roswell, Marshfleld, Mass alaignor, by memeassignments, to The Chase Shawna-t Company, Newlu rt, Masa, acorporation of Massachuset I Application December 22, 1945, Serial No.838,647

7 Claims. (CI. 2H7) The invention relates to snap action electricswitches. It is particularly concerned with a snap action switch ofsmall dimensions, positive in action, and capable of belng manufacturedat a price low enough to permit use in installations where switches ofthis type are desirable but where, heretofore, they have not been usedbecause of the high cost, large size, or limited life.

The switch is particularly useful in installations where operatingpressures do not have to be within close limits. For example, in thecase of a manually operated switch, it is obviously immaterial whetherthe force required is somewhat greater or less. Such a situation'wouldbe found in a radio switch. The user will not be particularly concernedwhether the switch operates with slightly more or less force. On theother hand, however, the functional parts of the switch of the presentinvention may be made with such accuracy and uniformity that switchesmade according to particular specifications will be substantiallyuniform in operating characteristics.

The construction functions with very slight movement of the operativemember but at the same time the extent of separation of the contactswill be sumcient to permit use with alternating current circuits up toapproximately ten amperes. The switch, of course, can be used withdirect current if the voltage and amperage are such that sparking andattendant fusing of the contacts are eliminated. T

It will be understood. of course, that the switches may be of the singlepole single throwor single pole double throw type. If of the single polesingle throw type. switches may be arranged to be either normally openor normally closed. In both cases. however, the movement of the switchblade is of the same general character, although the activating forcemay be applied at different areas, depending upon the normal stableposition of the blade. In one case, normally open position may beobtained simply by reversing the contacts, while in the other, thecontacts may remain in the same relationship with the stable position ofthe blade reversed.

The invention also includes the speciflc construction of the. movableswitch member with particular reference to the form thereof and themethod of achieving this formation. Other advantages of the switch willbe disclosed and will become more apparent as the description proceedswith the aid of the accompanying drawings. in which Fig. 1 is anisometric perspective of a typical form of the switch considerablyenlarged.

Fig. 2 is a front elevation of the switch shown in Fig. 1, with theinterior parts in dotted line.

Fig. 3 is a front elevation of a switch similar to Fig. 1, but having inaddition a third contact.

Fig. 4 is a front elevation of a switch similar to Fig. 1, but with twooppositely disposed terminals.

Fig. 5 is a section on the line H of Fig. 4, showing the switch innormal closed position.

Fig. 6 is a section on the line i-5 of Fig. 4, showing the switch inoperated open position.

Fig. 7 is a section on the line 1-1 of Fig. 2 with the contacts closed.

Fig. 8 is a plan view of the formed switch blade used in Fig. 4.

Fig. 9 is a. section on the line 8! of Fig. 8.

Fig. 10 is a section on the line llll of Fig. 8.

Fig. 11 is a plan view of a modified type of switch blade.

Fig. 12 is a section on the line l2-I2 of Fig. 11.

Fig. 13 is a section on the line lli3 of Fig. 11.

Fig. 14 is a side elevation of a normally open switch.

Fig. 15 is a section on line 15-" of Fig. 14.

Fig. 16 is a section on the line lll5 of Fig. 14 after the switch hasbeen closed.

A typical switch incorporating the present invention is shown in Fig. 1.In this figure the outer mately one-quarter inch. The dimensions,however, may be varied at will, and -it is not intended to limit theinvention in any way by the reference to specific size. The statement ofparticular dimensions is made merely to make it clear that a switch canbe made according to the present invention small enough in be used ininstallations where heretofore quick action switches of this generaltype were precluded because of their larger size or greater cost.

The switch consists generally of a housing 2 formed in two separateparts I and t to permit easy assembling of the interior operatingmechanism. The top half 4 of the housing has a cylindrical boss I boredto receive and operating pin it, the inner end of which is located topress against the'switch mechanism.

A shallow groove l2 extends down the two sides and across the bottom ofthe switch housing. This groove is adaptedto receive a. U-shaped bandwhich may be utilized in securing the switch to the structure with whichthe switch is to be used. Other attaching means may, of course, be usedas required without affecting the switch operation in any way.

The switch may be arranged to have two terminals l4 and i6, as shown inFig. 2, three terminals i8, 20 and 22, as shown in Fig. 3, or twoterminals 24 and 26 arranged opposite each other, as in Fig. 4. Allterminals are recessed in the housing to prevent rotation.

When the arrangement of Fig. 2 is used, the circuit will be broken atboth terminals, thereby providing an air gap equal to twice the switchopening. In Fig. 3 the arrangement provides for dividing the circuitthrough the use of the common terminal 22 and the terminals i8 and 20leading to two different circuits. In Fig. 4 the circuit is made andbroken at a single point so that the air gap is equal only to themovement of the operating member.

Figs. 5 and 6 show the general nature of the switch mechanism. A leafspring 30, two different forms of which are shown in Figs. 8 and 11, issecured to the bottom half 6 of the housing by means of a rivet 32. Thisrivet in addition fastens terminal 26 on the under side of the housing.In the forms of Figs. -2 and 3 the terminal 26 is omitted. In general,leaf spring 30 is in the form of a flat truncated cone with a raisedportion between its support 32 and the central cut away area. Theconstruction of leaf spring 38 will be described in detail hereinafter.In all forms, however, pressure on the raised area 34 will cause thecontact end to snap upwardly to the position shown in Fig. 6, once thecritical pressure has been reached, and all other parts of the leafspring substantially reverse themselves.

Pressure is brought to bear on area 34 by operating pin l0. Pin I ismade of insulating material, with its lower end engaging the elevatedarea 34 of the leaf spring 30, as shown in Figs. and 6. Leaf spring 38may have any number of contacts on its movable end. Ordinarily a singlecontact 38, as shown in Figs. 4, 5, 6, 8 and 10, or two contacts 42 and44, as shown in Figs. 2, 3, 7, 11, 12 and 13, will be used.

In the single contact construction, movable contact 38 is normally inengagement with fixed contact 40, located in line with rivet 32. In thetwo-contact construction movable contacts 42 and 44 shown in Fig. 11 arein engagement with corresponding fixed contacts located thereunder andindicated at 46 and 48 in Fig. 2 and at 50 and 52 in Fig. 3. Thetwo-contact arrangement is also shown in Fig. '7, which is a section onthe line of Fig. 2.

Contacts 46 and 48 in Fig. 2 are electrically associated with terminalsl4 and I6, contacts 60 and 52 are similarly connected with terminals i8and 20 in Fig. 3, and contact 40 of Fig. 4 is connected with terminal24. When operating pin I8 is pressed downwardly against the elevatedarea of the leaf spring as at 34 in Fig. 8, or at 56 in Fig. 11, a pointwill be reached where the pressed-upon area will snap downwardly and thecontact end of the leaf spring will snap upwardly substantiallyinstantaneously. The circuit of which the switch is a part is therebybroken very .quickly and sparking is held at a minimum. It

will be observed that this arrangement results in the contacts beingmaintained at an increasing pressure until the instant that the circuitis broken. From an electrical standpoint this is ver desirable and theswitch has been found to operate satisfactorily on 110-volt alternatingtion shown in Fig. 6 with the circuit broken.

Upward movement is limited by the stop 58. In this open position, theleaf spring will not be stable, and will remain there only so long aspressure on operating pin ill is exerted. As soon as the pressure on pinIII is released, leaf spring 30 will snap downwardly to the positionshown in Fig. 5, thereby reciosing the circuit.

The switch mechanism may also be arranged to provide a normally openswitch instead of the normally closed switch heretofore described. Onemethod of providing a normally open switch is to incorporate in theupper half 4 of the housing the fixed contacts 40, 46, 48, 50 and 52. Insuch cases, the contacts on the leaf spring would be placed on the upperside. As the stable position of the leaf spring is downward, as shown inFig. 5, the switch would thus be normally open. Pressure on pin l0 wouldresult in leaf spring 30 snapping upwardly, as shown in Fig. therebyclosing the contacts. long as pin I0 is held down, the contacts remainclosed, but as the leaf spring is unstable in this position, release ofpin in will cause reopening of the circuit as the leaf spring snapsdownwardly. In this arrangement, the direction of the pressure of pin inis opposite to the direction of movement of the free end.

Another arrangement of a normally open switch incorporating the presentinvention is shown in Figs. 14, 15 and 16. In this construction leafspring 30 is anchored in the housing so that in its stable position thecontact end is upward. Area 34 is in downward position while the sidelegs 66 and 68 are sprung upwardly.

Contact 38 is on the under side of the leaf spring, and fixed contact 40is in the same position as shown in Figs. 5 and 6. In this construction,it is contemplated that the switch when closed will have the leaf springin unstable position, so that reopening will take place as soon as thepressure on the operating pin is released.

The operating pin 16 has dual engaging members, l8 and 80. Thus, insteadof engaging leaf spring 30 at a single point along the axis, pin 16engages it at two laterally spaced points 82 and 84 near the bases ofthe legs 66 and 68. When downward pressure is exerted against the sidesof leaf spring 38 by members "and 80, the center area 34 will snapupwardly as the side legs 66 and 68 spring downwardly. Thecross-sectional upward curvature of the blade shown in Fig. 15 with theswitch open reverses itself to a downward curvature with the switchclosed, as shown in Fig. 16. The pressure on pin I6, causing closure ofthe switch, is in the direction of movement of the contact end. Thus itis evident that the greater the force applied to pin 16, the greater thepressure between contacts 38 and 40. It is unnecessary and undesirableto provide a stop above the movable end of leaf spring 30, as thegreater the upward movement of the free end, the farther apart thecontacts will be. Pin 16 is held against rotation by the crosswise guide11.

The particular longitudinal location of pin 16 is not critical. Theoperating characteristics of the leaf spring make it possible to locatepin Thecloserpressuremembersltandllareto' the mounting end of the blade,the faster the switch action will be, the less the vertical movement ofpin It, and the greater the operating force. As the presure members Itand OI are moved toward the contact end of spring blade 30, the switchaction will be slower, more travel of the operating pin will benecessary, and the operating force will be 1.

The provision of a normally open switch by reversing the contacts shownin Figs. and 6, orbyreversingtheleafspringandaddingmeans for on thesides of the leaf spring as shown in Figs. 14, and 16, requires nomodiilcation of the leaf spring or blade, and the character of theaction is substantially identical. whether the operating force beapplied at a single point on the longitudinal axis or at onpositeldisposed points on the legs.

The leaf spring 01' blade which constitutes the operating mechanism ofthe switch is preferably made from a thin sheet of beryllium copper. Thebladeis relatively wide in comparison to its length. when viewed in thelight of leaf springs on snap action switches of the prior art. As shownin Figs. 8 and 11, the center portion is cut away in what might betermed a keyhole formation. This produces short acutely tapered legs 88and 68 and a relatively narrow end cross bar. 82, both of which featuresare essential to proper snap action in a stubby blade of the typedisclwed. For the purpose of definition, the cross-bar I may beconsidered that portion extending the width of plate which carries thecontacts and which connects with the ends of the tapered legs. Thespring is deformed to a generally fiat truncated cone shape with thearea jmt below the bottom of the keyhole opening raised. The raisedareas are indicated at 34 in Fig. 8 and II in Fig. 11. Various methodsof shaping the leaf spring may be used. To produce the construction ofFigs. 8, 9 and 10 the spring may be placed between suitable dies whichwill distort the metal to the degree desired. In Figs. 11, 12 and 13 thedistortion has been accomplished by arching vthe mid-section of the endcross bar 82, as indicated at I. This cames the legs It and 88 to bedrawn together slightly at one end, thereby buckling-the metal to raisethe area at It.

After the leaf spring or blade has been deformed in either of the twomanners above described, the spring will present a raised areaimmediately next to the cut-away area along the longitudinal axis, asindicated at u in Fig. 8 and at 56 in Fig. 11. These areas are thepreferred areas against which pressure ma be brought to cause the switchto operate. The construction, however, presents a band extending acrossthe entire width of the blade, which band tapers off in operatingeffectiveness toward either end. Appropriate pressure brought to bearagainst the band area of the blade will cause actuation.

The exact configuration of the side portions 8 may be varied somewhat,but it has been found by experiment that the disclosed constructionproduces very satisfactory snap action. The contacts 3| of Fig. 8 and 42and II of Fig. 11 are made independently of the leaf spring and thensecurely afiixed to the spring by riveting in the usual manner.

The extent to which the 1m spring adeu formed. as shown in Figs. 8, 9and 10, or the extent to which e legs 86 and 8. are drawn together bythe eformation of the cross bar 6!, as shown in Figs. 11, 12 and 13,determines the amount of force that must be applied by the operating pinII at 34 or 58 to cause the movable end of the leaf spring to snap awayfromits normal position. l'n'some switches'it will be preferable to havethe leaf spring operate under a light force, in which case thedeformation will not be as great as in the case where more force on theoperating pin is desired.

The fiat cone formation produced either by pressing the spring in diesor by drawing the legs together by deformation of the cross bar at theend, both as heretofore described, results in the leaf spring beingcurved downwardly transversely at both ends. This curvature is plainlyshown in Fig. '7. When pressure is applied to the areas 84 or 56,indicated in Fig. 8 or 1 1, to such an extent that the free end of thespring is caused to snap upwardly to break the circuit, the curvature ofthe free end then reverses itself, as shown by the dotted line positionin Fig. 7. This characteristic is advantageous because it results in agreater movement of contacts 44 and 42 away from fixed contacts 46 and48 than would otherwise be the case. Thus the switch may be used incircuits of higher voltage without sparking.

When the leaf spring 30 is deformed, as in Figs. 8 and 11, to createraised areas at 34 and 58, respectively, the legs 66 and 68 will slopelaterally in a downward direction, that is, the interior edges of thelegs will be higher than the outside edges. This condition isillustrated in Figs. 9, l0, l2 and 13. The tapering formation of legs iiand 68 assists in providing excellent snap action of the contact end ofleaf spring II when the necessary force has been applied at the raisedareas immediately below the cut away area. The legs and 68, in additionto sloping "laterally downward, are also curved downwardly along thelongitudinal edges, as indicated at i! in Fig. 9. v

The lower end of the central opening is preferably curved, as shown, asthis minimizes the possibility of splitting of the leaf spring afterlong repeated use. The holes II and 12 shown in Figs. 8 and 11 areprovided to permit insertion of the rivet which secures the fixed end ofthe leaf spring to the housing. The rivet head, while holding the end ofleaf spring 30 substantially fiat over a small area, nevertheless doesnot lower raised areas 34 and I8 appreciably, nor does it interfere withproper snap action.

The leaf spring construction heretofore described is secured to thehousing at one end alon its center line, as has heretofore been pointedout. It is due to this center line anchorage that the particularlydesirable snap action is obtained. By this arrangement, all four comersand the sides and ends are free to spring to their new reversedpositions with a minimum of restraining influence from the support.Thus, the new cone formation which the blade assumes after snapping tothe new open or closed position, as the case may be, is a substantialreversal of its initial shape. The center line anchorage gives greaterfreedom of action and more responsiveness in this type of constructionthan has been known heretofore. It should be pointed out that thisistrue even though the toed-in character of the legs, shown in Fig. 11.is brought about by a deformation of cross bar 2. Reversal of thecurvaanaooe ture of cross bar 62 takes place even though the center areaat 64 has been arched upwardly. Area 64 will bend in the oppositedirection to the extent necessary as freely as if the cross bar 62 wereundeformed.

The snap action characteristics created by the truncated cone formationare such that the stresses on the metal as the blade snaps from oneposition to the other are limited in degree. Thus, there is excellentresistance to fatigue and the switch will have adequate life in the usesto which it will be put.

In the construction of the spring blade shown in Fig. 8 it will be notedthat the originally flat blade has been deformed by a suitable die tobring it into a permanently deformed shape which has heretofore beendescribed as a very flat truncated cone. This can be seen from anobservation of Figs. 9 and 10. In this form the metal of the bladesurrounding the slot and particularly the metal surrounding the narrowend of the slot has been stretched beyond its elastic limit, therebybeing permanently deformed so that itcannot return to flat condition.Such snap action that occurs in use, however, does not cause the elasticlimit to be exceeded thereafter, and hence the blade has a very longlife. The extent of the compression of the material surrounding theopening in the blade and the corresponding stretching of the material onthe periphery as snap action occurs is well within the elastic limit.

The opening or slot in the blade that runs the length of the shortstubby legs is entirely unobstructed, and the inner tapered edges oflegs 66 and 68 are free to shift from an up to a down position as bladereversal takes places.

The blade being relatively wide with respect to its length causes thelegs to be short and stubby. This feature gives to the switch its mostdesirable characteristics. The short, stubby construction of the legsgives very high resistance to any chattering of the contacts under themost rigorous vibration. This is because the contact force exerted bythe short, stubby legs is inherently greater than that of blades of whatmight be considered normal proportions according to the prior art. Inaddition to resistance to vibration, switches using this stubby bladeconstruction have less tendency to bounce on closure, which addsconsiderably to the life of the switch. For the purpose of defining whatis meant by a leaf spring relatively wide in respect to its length, itis stated that any leaf spring in which the effective length is not morethan twice the effective width will be such a leaf spring blade as to bewithin the scope of this invention.

- The 'ease with which the deformation of the leaf spring may be variedto meet different operating conditions makes this switch adaptable foruse in many different types of installations. The resulting performancein all cases, however, is substantially the same, namely, that thecontacts are urged against each other with full pressure until theinstant of separation, at which time the breaking of the circuit issubstantially instantaneous.

When reference is made to the switch housing, it is contemplated thatthis includes any type or form of structure in or on which the operativeparts of the switch are mounted. It is not intended to limit the housingto a closed type, such as is shown in the drawings. The housing may besuch as to expose the mechanism to view, so that operating conditionsmay be observed. The

housing must, of course, hold the parts firmly in their proper relation.

While preferred forms of the invention have been disclosed anddescribed, it is to be understood that the invention is not to belimited thereby, but only by the appended claims.

I claim:

1. An electrical switch comprising a housing, a leaf spring within saidhousing and rigidly supported thereon at one end at a position locatedon the longitudinal axis of said leaf spring, the other end of said leafspring movable within said housing, said leaf spring formed of a thinsheet of metal relatively wide in respect to its length with part of itscenter area cut away to provide a single unobstructed slot along thesides of which are stubby side legs of non-uniform width and arelatively narrow flexible continuous crossbar at the movable endconnecting said legs, said cross-bar unsupported and free to flex onreversing movement of said leaf spring, a contact on said cross-bar, thesupported end of said leaf spring being of substantially the same widthas the contact carrying cross-bar and the side edges of said leaf springextending substantially at full width in the direction of the support topresent unsupported comer areas which extend laterally from said supportand which are free to flex up and down in cooperative movement withother parts of the leaf spring, a contact affixed to said housingadapted to be engaged by the contact on said cross-bar, said leaf sprinpermanently deformed in the general shape of a. very flat cone, meansmovable through said housing for applying pressure to said leaf springadjacent said support whereby when suflicient pressure is applied, themovable end of said leaf spring will snap away from its normal positionand the cone formation will freely and instantly partially reverseitself with the cross-bar and the supported end flexing in the reverseddirection from normal, means limiting the movement of the movable end ofsaid leaf spring so that it cannot reach a second position of stabilitywhereby when the pressure against said leaf spring is reducedsufliciently said leaf spring will snap back to its original stable coneformation.

2. An electrical switch comprising a housing, a leaf spring within saidhousing and rigidly supported thereon at one end at a position locatedon the longitudinal axis of said leaf spring, the

other end of said leaf spring movable within said housing, said leafspring formed of a thin sheet of metal relatively wide in respect to itslength with part of its center area cut away to provide a singleunobstructed slot along the sides of which are stubby side legs ofnon-uniform width and a relatively narrow flexible continuous cross-barat the movable end connecting said legs, said cross-bar unsupported andfree to flex on reversing movement of said leaf spring, a, contact onsaid cross-bar, the supported end of said leaf spring being ofsubstantially the same width as the contact carrying cross-bar and theside edges of said leaf spring extending substantially at full width inthe direction of the support to present unsupported corner areas whichextend laterally from said support and which are free to flex up anddown in cooperative movement with other parts of the leaf spring, acontact affixed to said housing adapted to be engaged by the contact onsaid cross-bar, said leaf spring permanently deformed to present araised area between the fixed support and the cut away area, means forapplying pressure to said leaf spring at the raised normal position, andmeans attached to said housing to limit movement of the movable end ofsaid leaf spring away from its normal position so that said leaf springcannot reach a second position 'of stability whereby when pressureagainst said area is reduced sufllciently, said movable end of said leafspring will snap back to normal position.

3. An electrical switch comprising a housing, a leaf spring within saidhousing and rigidly supported thereon at one end at a position locatedon the longitudinal axis of said leaf spring, the other end of said leafspring movable within said housing, said leaf spring formed of a thinsheet of metal relatively wide in respect to its length with part of itscenter area cut away to provide a single unobstructed slot along thesides of which are stubby side legs of non-uniform width and arelatively narrow flexible continuous cross-bar at the movable endconnecting said legs, said crossbar unsupported and free to flex onreversing movement of said leaf spring, a contact on said cross-bar, thesupported end of said leaf spring being of substantially the same widthas the contact carrying cross-bar and the side edges of said leaf springextending substantially at full width in the direction of the support topresent unsupported corner areas which extend laterally from saidsupport and which are free to flex up and down in cooperative movementwith otherparts of the leaf spring, a contact affixed to said housingadapted to be engaged by the contact on said cross-bar, said leaf springpermanently deformed to provide a raised critical area between the fixedsupport of said leaf spring and the cut away area, said legs slopinglaterally downwardly from their interior edges, means movable throughsaid housing for applying a downward force to said raised area wherebywhen sufllcient force is applied said raised area will snap downwardlyand the legs and movable end of said leaf spring will snap upwardly toopen or close said contacts, and means within said housing for limitingthe movement of the movable end of said leaf spring to prevent said leafspring from reaching another position of stability whereby said movableend of said leaf spring will return to its normal position upon releaseof the pressure applied to said raised area.

4. An electrical switch comprising a housing, a leaf spring within saidhousing and rigidly supported thereon at one end at a position locatedon the longitudinal axis of said leaf spring, the other end of said leafspring movable within said housing, said leaf spring formed of a thinsheet of metal relatively wide in respect to its length with part of itscenter area cut away to provide a single unobstructed slot along thesides of which are stubby side legs of non-uniform width, a relativelynarrow flexible continuous cross-bar at the movable end connecting saidlegs, said cross-bar unsupported and freeto flex on reversing movementof said leaf spring, a contact on said crossbar, the supported end ofsaid leaf spring being of substantially the same width as the contactcarrying cross-bar and the side edges of said leaf spring extending atsubstantially full width sufficiently in the direction of the support topresent unsupported corner areas which extend laterally from saidsupport and which are free to flex up and down in cooperative movementwith other parts of the leaf spring, a contact aflixed to said housingadapted to be engaged by the contact on 1'0 formed to be in the generalshape of a very flat truncated cone, pressure applying means operablethrough said housing, the apex of said cone facing away from saidpressure applying means, said pressure applying means adapted to applypressure to said leaf spring at two opposite symmetrically disposedareas at the bases of said legs whereby when sufllcient pressure isapplied simultaneously to said areas the movable end of said leaf springwill snap away from its normal open position and the truncated coneformation will partially reverse itself to cause engagement of saidcontacts, said fixed contact acting as a stop to limit the movement ofthe movable end of said leaf spring at a position of instability so thatwhen said pressure against said leaf spring is sufficiently reduced saidmovable end of said leaf spring will snap back to openposition as thetruncated cone formation reverts to a stable condition.

5. An electrical switch comprising a housing, a leaf spring within saidhousing and rigidly supported thereon at one end at a position locatedon the longitudinal axis of said spring, the end portion of said leafspring laterally adjacent the position at which it is secured on thelongitudinal axis extending laterally to an extent substantially equalto the width of the blade to present corner areas which are unsupportedand free to flex up or down in cooperative movement with the other partsof the leaf spring, the other end of said leaf spring movable withinsaid housing, said leaf spring formed of a thin sheet of metal cut awayin part of its center area to provide a single unobstructed slot alongthe sides of which are side legs and a relatively narrow flexiblecross-bar at the movable end connecting said legs, a contact amxed tosaid housing and a corresponding contact on said cross-bar adapted tomake and break the support with said fixed contact, said leaf springpermanently deformed in the general shape of a very flat cone and havinga sensitive area close to said support and means for applying pressureto said sensitive area whereby said leaf spring will be caused partiallyto reverse itself to change the relationship of said fixed and movablecontacts, the direction of movement of said pressure applying meansbeing opposite that of the resulting movement of the free end of saidleaf spring.

6. A leaf spring for use in a switch comprising a thin sheet of metalrelatively wide in respect to its length, said sheet cut away in itscentral area to provide a single unobstructed slot with a flexiblecross-bar extending across one end thereof, legs connected by saidcross-bar extending away therefrom along the sides of said sheet ofgradually increasing width, that portion of the sheet beyond said legsand cutway area being continuous from side to side and of substantiallythe same width as the cross-bar and extending to a positionsubstantially beyond said cut-away area. an aperture through said sheeton the longitudinal axis at a position where there will be corner areason both sides of said aperture, said sheet being permanently deformed inthe general shape of a very flat truncated cone whereby there will be araised area between said cut-away area and said aperture and midway ofsaid sides, said spring capable of substantially instantaneous completereversal of its cone form by the application of sufliclent pressure tocritical areas with corresponding bending of said crossbar and saidcorner areas.

said cross-bar, said leaf spring permanently de- 73A leaf spring for usein a switch, said leaf 1! spring formed from a thin sheet of metalrelatively wide in respect to its length, said sheet being cut away atits interior so as to provide a single unobstructed tapering slot toform a relatively narrow flexible cross-bar extending transversely atone end of said sheet, said leaf spring being of substantially uniformwidth over its entire length with the sides of one end commencingadjacent the end of said slot and the other ends of said sidesterminating a substantial distance beyond the other end of said slot, anaperture through said leaf spring located on the longitudinal axis, saidaperture so positioned as to be spaced from the end of said slot and tohave corner areas on both sides thereof, said sheet permanently deformedin the shape of a,

very flat truncated cone whereby upon suitable pressure being applied tosensitive areas of said sheet said cross-bat. tapered 1888, and cornerI2 areas will flex in reversed direction 'irom normal to causesubstantially instantaneous reversal of the cone formation.

EARLE R- ROSWELL.

